1. Field of the Invention
The present invention relates to a pharmaceutical vehicle. More particularly, the present invention relates to a pharmaceutical vehicle excellent in the property of gradually releasing an active ingredient.
2. Description of the Prior Art
Various gradually releasing pharmaceutical compositions have been known, but most of them are used for oral administration and gradually releasing suppository compositions have hardly been known.
Recently, various attempts have been made to cure tumors by applying suppositories containing effective carcinostatic ingredients to the rectum, the uterus cervix, the vagina, the urethra and the like to allow the effective ingredients to act on the affected parts for a long time. For example, for remedy of uterine cancer, the effective ingredient is applied to the affected part once a day. Furthermore, in case of cancer of the rectus, it is necessary to apply the effective ingredient once a day because evacuation is ordinarily made once a day. Thus, suppositories of carcinostatic agents are ordinarily applied once a day. Therefore, development of a pharmaceutical vehicle for such suppositories capable of releasing the effective ingredient in about 24 hours has been desired.
Suppositories comprising a fatty acid glyceride as the vehicle are known. Since these suppositories are arranged so that the vehicle is molten by the body temperature to release the effective ingredient, a fatty acid glyceride having a melting point lower than the body temperature (37.degree. C.) is used as the vehicle. Therefore, in scores of minutes after application of these suppositories, the vehicle is molten and the effective ingredient is released in a relatively short time. In short, these suppositories have not a property of gradually releasing the effective ingradient. Furthermore, when the effective ingredient has to be included at a high concentration, the area around the affected part becomes inflamed.
Suppositories comprising a carboxyvinyl polymer as the vehicle are known as gradually releasing suppositories. These suppositories, however, are defective in that the speed of releasing the effective ingredient is too low or the effective ingredient is not sufficiently released.